# US 9,040,598 B2 · Renewable polyester compositions having a low density

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- Number: US 9,040,598 B2
- Document ID: US9040598B2
- Status: Granted
- Kind: B2
- Application number: 13/370,883
- Filed: 2012-02-10
- Published: 2013-08-15
- Granted: 2015-05-26
- Earliest claimed: 2012-02-10
- Assignees: Kimberly-Clark Worldwide, Inc.
- Applicants: Neil T. Scholl; Ryan J. McEneany; Thomas A. Eby; Vasily A. Topolkaraev
- Inventors: Neil T. Scholl; Ryan J. McEneany; Thomas A. Eby; Vasily A. Topolkaraev
- Web page: https://patentgrep.com/patent/US9040598B2

## CPC

- C08L 67/04: Polyesters derived from hydroxycarboxylic acids, e.g. lactones (C08L67/06 takes precedence)
- C08L 23/02: not modified by chemical after-treatment
- C08L 33/00: Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides or nitriles thereof; Compositions of derivatives of such polymers
- C08L 63/00: Compositions of epoxy resins; Compositions of derivatives of epoxy resins
- C08L 67/00: Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain (of polyester-amides C08L77/12; of polyester-imides C08L79/08); Compositions of derivatives of such polymers
- C08L 71/00: Compositions of polyethers obtained by reactions forming an ether link in the main chain (of polyacetals C08L59/00; of epoxy resins C08L63/00; of polythioether-ethers C08L81/02; of polyether-sulfones C08L81/06); Compositions of derivatives of such polymers
- C08L 23/0815: {with aliphatic 1-olefins containing one carbon-to-carbon double bond}
- C08L 23/10: Homopolymers or copolymers of propene
- C08L 2205/02: containing two or more polymers of the same C08L -group
- C08L 2205/03: containing three or more polymers in a blend
- C08L 2207/04: Thermoplastic elastomer
- C08L: COMPOSITIONS OF MACROMOLECULAR COMPOUNDS (compositions based on polymerisable monomers C08F, C08G; artificial filaments or fibres D01F; textile treating compositions D06)

## Abstract

A thermoplastic composition that contains a rigid renewable polyester and has a voided structure and low density is provided. To achieve such a structure, the renewable polyester is blended with a polymeric toughening additive to form a precursor material in which the toughening additive can be dispersed as discrete physical domains within a continuous matrix of the renewable polyester. The precursor material is thereafter stretched or drawn at a temperature below the glass transition temperature of the polyester (i.e., “cold drawn”). This creates a network of voids located adjacent to the discrete domains, which as a result of their proximal location, can form a bridge between the boundaries of the voids and act as internal structural “hinges” that help stabilize the network and increase its ability to dissipate energy. The present inventors have also discovered that the voids can be distributed in a substantially homogeneous fashion throughout the composition.

## Claims

### Claim 1

A thermoplastic composition comprising at least one rigid renewable polyester having a glass transition temperature of about 0° C. or more, at least one polymeric toughening additive, at least one interphase modifier, wherein the interphase modifier is present in an amount ranging from about 0.5 wt. % to about 15 wt. % based on the weight of the renewable polyester, and a polyepoxide modifier having a number average molecular weight of from about 7,500 grams per mole to about 250,000 grams per mole, wherein the thermoplastic composition has a morphology in which a plurality of discrete primary domains and voids are dispersed within a continuous phase, the domains containing the polymeric toughening additive and the continuous phase containing the renewable polyester, wherein the thermoplastic composition has a density of about 1.4 grams per cubic centimeter or less, and wherein the average percent volume of the composition that is occupied by the voids is from about 30% to about 70% per cubic centimeter.

### Claim 2 (depends on 1)

The thermoplastic composition of claim 1, wherein the composition has a density of from about 0.5 grams per cubic centimeter to about 0.95 grams per cubic centimeter.

### Claim 3 (depends on 1)

The thermoplastic composition of claim 1, wherein the average percent volume of the composition that is occupied by the voids is from about 40% to about 60% per cubic centimeter.

### Claim 4 (depends on 1)

The thermoplastic composition of claim 1, wherein the aspect ratio of the voids is from about 0.1 to about 1.

### Claim 5 (depends on 1)

The thermoplastic composition of claim 1, wherein the voids contain a combination of micro-voids and nano-voids.

### Claim 6 (depends on 1)

The thermoplastic composition of claim 1, wherein the renewable polyester is a polylactic acid.

### Claim 7 (depends on 1)

The thermoplastic composition of claim 1, wherein the renewable polyester has a glass transition temperature of from about 50° C. to about 75° C.

### Claim 8 (depends on 1)

The thermoplastic composition of claim 1, wherein the ratio of the solubility parameter for the renewable polyester to the solubility parameter of the polymeric toughening additive is from about 0.5 to about 1.5, the ratio of the melt flow rate for the renewable polyester to the melt flow rate of the polymeric toughening additive is from about 0.2 to about 8, and the ratio of the Young's modulus elasticity of the renewable polyester to the Young's modulus of elasticity of the polymeric toughening additive is from about 2 to about 500.

### Claim 9 (depends on 1)

The thermoplastic composition of claim 1, wherein the polymeric toughening additive includes a polyolefin.

### Claim 10 (depends on 9)

The thermoplastic composition of claim 9, wherein the polyolefin is a propylene homopolymer, propylene/α-olefin copolymer, ethylene/α-olefin copolymer, or a combination thereof.

### Claim 11 (depends on 1)

The thermoplastic composition of claim 1, wherein the interphase modifier has a kinematic viscosity of from about 0.7 to about 200 centistokes, determined at a temperature of 40° C.

### Claim 12 (depends on 1)

The thermoplastic composition of claim 1, wherein the interphase modifier is hydrophobic.

### Claim 13 (depends on 1)

The thermoplastic composition of claim 1, wherein the interphase modifier is a silicone, silicone-polyether copolymer, aliphatic polyester, aromatic polyester, alkylene glycol, alkane diol, amine oxide, fatty acid ester, or a combination thereof.

### Claim 14 (depends on 1)

The thermoplastic composition of claim 1, wherein the polymeric toughening additive constitutes from about 1 wt. % to about 30 wt. % based on the weight of the renewable polyester.

### Claim 15 (depends on 1)

The thermoplastic composition of claim 1, wherein the polyepoxide modifier includes an epoxy-functional (meth)acrylic monomeric component.

### Claim 16 (depends on 1)

The thermoplastic composition of claim 1, wherein the renewable polyester constitutes about 70 wt. % or more of the thermoplastic composition.

### Claim 17 (depends on 1)

The thermoplastic composition of claim 1, wherein the composition exhibits a Poisson coefficient of about 0.1 or less.

### Claim 18 (depends on 1)

The thermoplastic composition of claim 1, wherein the composition exhibits an Izod notched impact strength of about 1 J/cm or more, measured at 23° C. according to ASTM D256-10 (Method A).

### Claim 19 (depends on 1)

The thermoplastic composition of claim 1, wherein the composition exhibits a tensile elongation at break of about 40% or more, measured at 23° C. according to ASTM D638-10.

### Claim 20 (depends on 1)

The thermoplastic composition of claim 1, wherein the composition has an average surface roughness of about 0.2 μm or more.

### Claim 21

A method for forming a low density thermoplastic composition for use in a molded article, the method comprising:
forming a blend that contains a rigid renewable polyester, at least one polymeric toughening additive, at least one interphase modifier, wherein the interphase modifier is present in an amount ranging from about 0.5 wt. % to about 15 wt. % based on the weight of the renewable polyester, and a polyepoxide modifier having a number average molecular weight of from about 7,500 grams per mole to about 250,000 grams per mole, wherein the rigid renewable polyester has a glass transition temperature of about 0° C. or more;
forming a precursor material from the blend; and
stretching the precursor material at a temperature that is lower than the glass transition temperature of the renewable polyester to form a thermoplastic composition that contains a plurality of discrete primary domains and voids dispersed within a continuous phase, the domains containing the polymeric toughening additive and the continuous phase containing the renewable polyester, wherein the thermoplastic composition has a density of about 1.4 grams per cubic centimeter or less, further wherein the average percent volume of the composition that is occupied by the voids is from about 30% to about 70% per cubic centimeter.

### Claim 22 (depends on 21)

The method of claim 21, further comprising molding the thermoplastic composition into the shape of an article.

### Claim 23 (depends on 22)

The method of claim 22, wherein the thermoplastic composition is injection molded into the shape of the article.

### Claim 24 (depends on 22)

The method of claim 22, further comprising annealing the composition after molding at a temperature that is above the glass transition temperature of the renewable polyester.

### Claim 25 (depends on 21)

The method of claim 21, wherein the composition has a density of from about 0.5 grams per cubic centimeter to about 0.95 grams per cubic centimeter.

### Claim 26 (depends on 21)

The method of claim 21, wherein the renewable polyester is a polylactic acid.

### Claim 27 (depends on 21)

The method of claim 21, wherein the polymeric toughening additive includes a propylene homopolymer, propylene/α-olefin copolymer, ethylene/α-olefin copolymer, or a combination thereof.

### Claim 28 (depends on 21)

The method of claim 21, wherein the polyepoxide modifier includes an epoxy-functional (meth)acrylic monomeric component.

### Claim 29 (depends on 21)

The method of claim 21, wherein the precursor material is stretched to a draw ratio of from about 1.1 to about 3.0.

### Claim 30 (depends on 21)

The method of claim 21, wherein the precursor material is stretched at a temperature at least about 10° C. below the glass transition temperature of the renewable polyester.

### Claim 31 (depends on 21)

The method of claim 21, wherein the blend is generally free of gaseous blowing agents.